I'm traveling to London in a few days and a had a few questions about charging my iPhone. I have the adapter for the plugs however do i need an power inverter? Can the iphone handle an input of 220-240V instead of the 110-120V in North America? i'm sure it says it on the iphone charger however i can't read mine. the gray text on a gray background mixed with small font size make is hard to read.